mirror of https://github.com/F-Stack/f-stack.git
97 lines
2.6 KiB
ReStructuredText
97 lines
2.6 KiB
ReStructuredText
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.. SPDX-License-Identifier: BSD-3-Clause
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Copyright(c) 2018 Ericsson AB
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Distributed Software Eventdev Poll Mode Driver
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==============================================
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The distributed software event device is an eventdev driver which
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distributes the task of scheduling events among all the eventdev ports
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and the lcore threads using them.
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Features
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--------
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Queues
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* Atomic
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* Parallel
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* Single-Link
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Ports
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* Load balanced (for Atomic, Ordered, Parallel queues)
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* Single Link (for single-link queues)
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Configuration and Options
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-------------------------
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The distributed software eventdev is a vdev device, and as such can be
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created from the application code, or from the EAL command line:
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* Call ``rte_vdev_init("event_dsw0")`` from the application
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* Use ``--vdev="event_dsw0"`` in the EAL options, which will call
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rte_vdev_init() internally
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Example:
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.. code-block:: console
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./your_eventdev_application --vdev="event_dsw0"
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Limitations
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-----------
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Unattended Ports
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~~~~~~~~~~~~~~~~
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The distributed software eventdev uses an internal signaling schema
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between the ports to achieve load balancing. In order for this to
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work, the application must perform enqueue and/or dequeue operations
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on all ports.
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Producer-only ports which currently have no events to enqueue should
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periodically call rte_event_enqueue_burst() with a zero-sized burst.
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Ports left unattended for longer periods of time will prevent load
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balancing, and also cause traffic interruptions on the flows which
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are in the process of being migrated.
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Output Buffering
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~~~~~~~~~~~~~~~~
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For efficiency reasons, the distributed software eventdev might not
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send enqueued events immediately to the destination port, but instead
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store them in an internal buffer in the source port.
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In case no more events are enqueued on a port with buffered events,
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these events will be sent after the application has performed a number
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of enqueue and/or dequeue operations.
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For explicit flushing, an application may call
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rte_event_enqueue_burst() with a zero-sized burst.
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Priorities
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~~~~~~~~~~
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The distributed software eventdev does not support event priorities.
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Ordered Queues
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~~~~~~~~~~~~~~
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The distributed software eventdev does not support the ordered queue type.
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"All Types" Queues
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~~~~~~~~~~~~~~~~~~
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The distributed software eventdev does not support queues of type
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RTE_EVENT_QUEUE_CFG_ALL_TYPES, which allow both atomic, ordered, and
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parallel events on the same queue.
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Dynamic Link/Unlink
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~~~~~~~~~~~~~~~~~~~
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The distributed software eventdev does not support calls to
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rte_event_port_link() or rte_event_port_unlink() after
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rte_event_dev_start() has been called.
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